1. Field of the Invention
The present invention relates to a coating solution for the formation of a high dielectric constant thin film and a method for the formation of a dielectric thin film using the coating solution. More specifically, the present invention relates to a coating solution for forming a high dielectric constant thin film which comprises a stabilized precursor, and a method for forming a high dielectric constant thin film by applying the coating solution to a substrate and drying the coated substrate at a low temperature.
2. Description of the Related Art
Semiconductor devices are becoming smaller in size and weight and more convergent. There is a strong tendency to embed semiconductor devices and the number of input/output terminals in semiconductor devices is increasing. Under these circumstances, a number of passive elements (including capacitors) capable of performing many functions in a defined capacity must be accommodated in the vicinity of active integrated circuit chips. Decoupling capacitors are used to stably supply an electric power to input terminals. In decoupling capacitors, an electric power region must be kept close to a ground region such that plane inductance and via inductance are reduced to extend low-impedance regions in a high frequency range.
To this end, embedding of decoupling capacitors under active integrated circuit chips is recognized as an optimal solution. In embedded capacitors using dielectric thin films, the dielectric thin films are formed within printed circuit boards positioned below active integrated circuit chips. As a result, an electric power region is as close as possible to a ground region so that the length of lines connected to the capacitors can be minimized to effectively reduce low-impedance regions in a high frequency range.
Continuous efforts have been made to minimize the area of embedded capacitors using high dielectric constant materials. Composite metal-oxide dielectrics, such as SrTiO3, BST and PLZT are currently known as the most useful materials for practical applications. For the practical applications of dielectric thin films using the materials, low-temperature formation of the dielectric thin films is required to improve the temperature characteristics of the dielectric thin films and make the dielectric thin films suitable for the fabrication of various kinds of semiconductor devices.
Dielectric thin films are formed by physical processes, e.g., vacuum evaporation, sputtering and laser abrasion, sol-gel processes based on the thermal decomposition of organometallic compounds, and chemical processes, e.g., chemical vapor deposition. Of these, sol-gel processes are most generally used from the standpoint of processing costs.
Japanese Unexamined Patent Publication No. Hei 7-37422 discloses a coating solution for forming a ferroelectric film and a method for forming a ferroelectric film using the coating solution by a sol-gel process wherein the coating solution comprises an organometallic compound represented by ATiO3 (where A=Ba, Sr, Ca, Mg or Pb) or Bi4Ti3O12 as a raw material, a β-diketone as a stabilizer, and hydrogen peroxide as an oxidant.
U.S. Pat. No. 5,776,788 discloses a method for forming a PZT dielectric film by a sol-gel process and a method for manufacturing a capacitor. According to this patent, a dielectric thin film is formed by preparing a coating solution containing an organometallic compound and an alkanolamine, drying the coating solution to form a thin film, and oxidatively sintering the thin film to obtain a perovskite crystal.
U.S. Pat. No. 5,593,495 discloses a method for manufacturing a thin film of composite metal-oxide dielectric by a sol-gel process. According to this method, a thin film is manufactured by spin coating a precursor solution on a substrate to form a thin film in a sol state, drying the thin film in the sol state to form a thin film of dry gel, and subjecting an obtained dry gel thin film to a heat treatment at 500 to 600° C. and crystallizing the obtained dry gel thin film.
According to the conventional methods, dielectric thin films are generally formed by a sol-gel process. Specifically, dielectric thin films are generally formed by spin coating a coating solution to a thin film, thermally decomposing the thin film at 300-400° C., and annealing the thin film at 600° C. or higher to crystallize the thin film.